1. Field of the Invention
The invention relates to a method for insertion of a weft thread on a weaving loom whereby an insertion parameter is determined. The invention also relates to a weaving loom for the application of such a method, in other words a weaving loom that applies a method as stated above.
2. Description of Related Art
Weaving looms in which compressed air is supplied to a blower comprise one or more main blowers and a number of secondary blowers for insertion of a weft thread into a weaving shed. On such weaving looms where different types of weft threads are inserted into a weaving shed according to a pattern, a corresponding set of main blowers with a corresponding supply device for compressed air is provided for each of these weft threads. The compressed air is supplied, for example, by an appropriate control of shut-off valves installed between a reservoir with compressed air and corresponding main blowers and/or secondary blowers. The amount of compressed air supplied can be regulated here by means of a motor-controlled throttle valve installed between the reservoir and a corresponding main blower and/or secondary blower. Such a motor-controlled throttle valve comprises for example a controllable stepping motor that can be controlled in both directions with a desired number of steps by means of a control unit.
The control of the amount of compressed air supplied during weaving as a function of a deviation from a measured insertion parameter is well known. It is possible here, for example, to control the amount of compressed air supplied in such a way that an inserted weft thread reaches the end of the weaving shed at a more or less desired angular position of the weaving loom. According to one possibility, a mean deviation is determined here between the moment at which the weft thread reaches the end of the weaving shed and the moment at which the mean drive shaft of the weaving loom reaches a given angular position. The throttle valve is then controlled, for example, in such a way that the mean deviation for insertions becomes more or less equal to a given value.
It is also possible to control the rotational speed of the weaving loom during weaving as a function of a deviation from a measured insertion parameter. For example, as described in NL 7908357 A, to control this rotational speed in such a way that the time required to insert a weft thread into a weaving shed takes a more or less constant proportion of the actual time for a weaving cycle determined by the rotational speed of the weaving loom. A weaving cycle is determined i.a. by a given time necessary for one revolution of the weaving loom, in other words by the weaving speed of the weaving loom or the rotational speed of the weaving loom. One weft thread is normally inserted into a weaving shed during one revolution of the weaving loom.